How is Uranus colder than Neptune

With Uranus at an average distance of 2.88 billion kilometres from the Sun and Neptune at an average distance of 4.5 billion kilometres it would be very easy to point out which of the gas giants is the coldest, but if you were you were to say that Neptune was the coldest, you’d be wrong.Given that we expect planets further from the Sun to be colder than those closer, this does make Neptune and Uranus quite a mysterious pair. Uranus and Neptune are brimming with volatiles such as water, methane and ammonia and due to their composition in comparison to Jupiter and Saturn, which are comprised mainly of hydrogen and helium, are labelled the ice giants. Scientists have measured how hot Uranus and Neptune should be and have found that Uranus is very cold and very dim